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Here’s some background on the concept: https://physics.aps.org/articles/v8/18

Basic idea is that you send out a microwave signal and at the same time send entangled microwaves/photons (in the microwave band) into a trap where they basically spin around “idling”/waiting for the potential weak signal to come back. You then feed both the returned signal which is super weak and the idled signal into a josephsen parametric converter. Basically an amplifier based upon a Josephsen junction. The result is that using that type of amplifier it amplifies signals that are quantum entangled more than it amplifies non entangled signals. And you get increased SNR on your signal you get back. So the microwave still has to hit the target and bounce back to you / receiver station you just can use a much weaker signal to transmit the microwave and as a result it acts similarly to passive radar that uses ambient RF to detects objects in the air.

Makes me wonder if this could be applied to cameras? With visible light instead of microwaves.
Don't understand it, but one guy interviewed on the subject said resolution is a function of all the entangled photons. That seems to mean you circumvent the diffraction limit.
I'm confused though, as it says the act of reflection destroys the entanglement? Is entanglement not a binary property though?
As far as I know such situations can be described by density matrices.

https://en.wikipedia.org/wiki/Density_matrix

First published result? There were reports of military work before: https://www.scmp.com/news/china/diplomacy-defence/article/21... This publication gave some credibility to the earlier reports of presumably classified work.
>The researchers go on to compare their quantum radar with conventional systems operating with similarly low numbers of photons and say it significantly outperforms them, albeit only over relatively short distances.

No rendering stealth aircraft obsolete just yet

Only over short distances? Is this because entangled photons decohere as they go longer?
Yes, exactly.
Some more recent discussion: https://hackaday.com/2019/08/26/quantum-radar-hides-in-plain...